JP2014095630A - Radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a noise caused by unnecessary reflected light, and to suppress the deterioration of the detecting accuracy of a radar device.SOLUTION: A radar device 1 includes: a light source 2 for emitting rays of light; an optical scanning part 7 for scanning the rays of light by rotating a mirror 71 with a rotary shaft 72 as a center; a polarized beam splitter 5 having a function for transmitting the rays of light in a predetermined polarizing direction, and for reflecting the rays of light in any direction other than the predetermined polarizing direction; a 1/4 wavelength plate 6 having a function for converting linearly polarized light into circularly polarized light, and for converting the circularly polarized light into the linearly polarized light; a light detector 9 for detecting the incident rays of light; and an aperture 4 disposed on a path on which the rays of light emitted from the light source 2 pass before getting to the polarized beam splitter 5 for allowing a part of the rays of light emitted from the light source 2 to pass, and for blocking the passage of the rays of light other than that part of the rays of light to reduce the diameter of the rays of light emitted from the light source 2.

Description

  The present invention relates to a radar apparatus that irradiates light and acquires information related to an object that reflects light based on the reflected light.

  Conventionally, when irradiation light passes through a radar apparatus in a radar apparatus that obtains information (for example, a distance to the object) about an object that reflects light by irradiating light and detecting light reflected by the object. There is known one employing a coaxial optical system in which the optical axis of the reflected light coincides with the optical axis when the reflected light passes through the radar device.

  However, in a radar device that employs a coaxial optical system, unnecessary reflected light that is generated when reflected light that passes through the radar device is reflected by the components of the radar device is detected as noise by a photodetector in the radar device. The detection accuracy of the radar apparatus may be reduced.

  In order to solve such a problem, a technique is known in which a through hole through which light emitted from a light source passes is formed in a mirror that further reflects light reflected by an object toward a photodetector (for example, , See Patent Document 1).

JP 2004-28598 A

  However, in the technique described in Patent Document 1, since a through hole is formed in the mirror, a part of the light reflected by the object cannot be reflected toward the photodetector. As a result, there is a problem in that the amount of reflected light detected by the photodetector is reduced and the detection accuracy of the radar apparatus is lowered.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique for reducing noise caused by unnecessary reflected light and suppressing a decrease in detection accuracy of a radar apparatus.

  The present invention, which has been made to achieve the above object, is irradiated from a light source by rotating a light source for irradiating light and a reflecting member having a function of reflecting light around a predetermined rotation axis. A scanning unit that scans light, and a path through which light emitted from the light source passes to reach the scanning unit, transmits light in a predetermined polarization direction that is set in advance and reflects light in a direction other than the predetermined polarization direction A first functional member having a function of allowing the light to pass through the first functional member until it reaches the scanning unit, and converts linearly polarized light into circularly polarized light and converts circularly polarized light into linearly polarized light. A second functional member having a function to perform, a light detection unit that is disposed on a path through which light that is incident on the first functional member and reflected by the first functional member passes from the scanning unit side, and that detects the incident light, The light emitted from the light source It is arranged on the path that passes to reach the functional member, and while passing a part of the light emitted from the light source, it prevents the light emitted from the light source by blocking the passage of light other than the part. A radar apparatus comprising: a throttle member that squeezes the diameter.

  In the radar apparatus configured in this way, first, part of the light emitted from the light source passes through the diaphragm member, and the passage of light other than this part is blocked by the diaphragm member, so that the light source The diameter of the irradiated light is reduced and light is emitted from the aperture member.

  Further, among the light emitted from the aperture member, light having a predetermined polarization direction passes through the first functional member and passes through the second functional member. As a result, the light is converted from linearly polarized light into circularly polarized light and reaches the scanning unit. And the light which reached | attained the scanning part is irradiated as a radar wave toward the direction according to the scanning angle of a reflection member.

  Thereafter, when light reflected by the object (hereinafter also referred to as reflected light) reaches the scanning unit, it is reflected by the reflecting member and passes through the second functional member again. Thereby, the reflected light is converted from circularly polarized light into linearly polarized light and reaches the first functional member.

  In addition, the polarization direction of the reflected light converted into the linearly polarized light by the second functional member is shifted by 90 ° with respect to the polarization direction of the light before being converted into the circularly polarized light irradiated from the light source. For this reason, the reflected light that has reached the first functional member is reflected by the first functional member, reaches the light detection unit, and can detect an object that reflects the radar wave. Moreover, the distance to the object which reflected light can be measured based on the difference of the time when the light source irradiated light, and the time when the light detection part detected reflected light.

  Then, by reducing the light so that the aperture of the light emitted from the light source falls within the diameter of the reflecting member that reflects the light, the noise caused by unnecessary reflected light that is reflected outside the diameter of the reflecting member. Can be reduced.

  Further, the diaphragm member is disposed on a path through which light emitted from the light source passes to reach the first functional member. For this reason, when light that has entered the diaphragm member from the light source and is blocked from passing is reflected by the diaphragm member, the reflected light is a path through which the light reflected by the first functional member passes through the diaphragm member. It goes in the direction opposite to the photodetection unit arranged above. As a result, unnecessary reflected light generated when light emitted from the light source enters the diaphragm member is suppressed from being detected as noise by the light detection unit in the radar device, and noise caused by unnecessary reflected light is reduced. can do.

  Furthermore, noise due to unnecessary reflected light can be reduced without forming a through hole in the first functional member, and a decrease in detection accuracy of the radar apparatus can be suppressed.

It is a figure which shows the structure and operation | movement of the radar apparatus 1 of 1st Embodiment. It is a figure which shows the structure and operation | movement of the radar apparatus 1 of 2nd Embodiment. It is a side view which shows the structure of the polarizing beam splitter 100 and aperture 200 of 3rd Embodiment. It is a side view which shows the structure of the polarizing beam splitter 300 and the aperture 200 of 4th Embodiment.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the radar apparatus 1 includes a light source 2, a collimating lens 3, an aperture 4, a polarizing beam splitter 5, a quarter wave plate 6, an optical scanning unit 7, a light receiving lens 8, and a photodetector 9, and these And a housing 10 for storing the constituent elements.

The light source 2 is composed of, for example, a semiconductor laser diode and irradiates linearly polarized pulsed laser light as a radar wave.
The collimating lens 3 converts the laser light emitted from the light source 2 into parallel light and irradiates the aperture 4 toward the aperture 4.

  The aperture 4 is a plate-shaped member 41 having an opening 42 formed in part, and is disposed between the collimating lens 3 and the polarization beam splitter 5. As a result, the aperture 4 reflects the laser light incident on the region other than the opening 42 in the incident surface 43 on which the laser light is incident, and passes the laser light incident on the region inside the opening 42. That is, the laser light incident on the aperture 4 from the collimator lens 3 is shaped into the shape of the opening 42 and is irradiated toward the polarization beam splitter 5.

  The polarization beam splitter 5 has a function of transmitting a component having a predetermined polarization direction in the laser light incident on the polarization beam splitter 5 from the aperture 4 and reflecting a component having a polarization direction other than the predetermined polarization direction. Have.

  The polarization beam splitter 5 is arranged so that the predetermined polarization direction matches the polarization direction of the laser light emitted from the light source 2. Further, the polarizing beam splitter 5 is a cube type formed by sticking right-angle prisms into a cube shape. At an angle A1). In the present embodiment, the inclination angle A1 is 45 °.

The quarter-wave plate 6 has a function of converting linearly polarized light into circularly polarized light and converting circularly polarized light into linearly polarized light, and is disposed between the polarizing beam splitter 5 and the optical scanning unit 7.
The optical scanning unit 7 is set in advance to scan the laser light incident from the quarter-wave plate 6 by vibrating the mirror 71 that reflects the laser light around the rotation shaft 72 provided on the mirror 71. The scanning angle range R1 is used.

The light receiving lens 8 guides the laser beam incident from the optical scanning unit 7 side and reflected by the polarization beam splitter 5 to the photodetector 9.
The photodetector 9 is composed of, for example, a photodiode, and detects the laser light incident from the light receiving lens 8.

Next, a method for detecting an object reflecting a radar wave in the radar apparatus 1 configured as described above will be described.
First, the laser light emitted from the light source 2 is converted into parallel light by the collimating lens 3, and the diameter of the light is further reduced by the aperture 4 to reach the polarization beam splitter 5 (see the light L <b> 1).

  Then, the laser light reaching the polarizing beam splitter 5 passes through the polarizing beam splitter 5 and further passes through the quarter wavelength plate 6. As a result, the laser light is converted from linearly polarized light to circularly polarized light, and reaches the optical scanning unit 7 (see the light L2).

Then, the laser beam that has reached the optical scanning unit 7 is reflected by the mirror 71 and is irradiated as a radar wave in a direction corresponding to the scanning angle of the mirror 71 (see the light L3).
Thereafter, when laser light reflected by the object B (hereinafter also referred to as reflected laser light) reaches the optical scanning unit 7 (see the light L4), it is reflected by the mirror 71 and passes through the quarter wavelength plate 6 again (see FIG. 4). See light L5). As a result, the reflected laser light is converted from circularly polarized light into linearly polarized light and reaches the polarization beam splitter 5 (see the light L5).

  The polarization direction of the reflected laser light converted into linearly polarized light by the quarter wavelength plate 6 is shifted by 90 ° with respect to the polarization direction of the laser light before being irradiated from the light source 2 and converted into circularly polarized light. For this reason, the reflected laser light that has reached the polarizing beam splitter 5 is reflected by the polarizing beam splitter 5 and irradiated toward the light receiving lens 8 (see the light L6). Thereby, the reflected laser beam reaches the photodetector 9, and the object that reflects the radar wave can be detected.

Moreover, the distance to the object which reflected the laser beam can be measured based on the difference between the time when the light source 2 irradiated the pulse laser beam and the time when the photodetector 9 detected the reflected laser beam.
In the radar apparatus 1 configured as described above, the aperture 4 reduces the laser beam so that the aperture of the laser beam emitted from the light source 2 falls within the mirror diameter of the mirror 71 that reflects the laser beam. Noise caused by unnecessary reflected light reflected outside the mirror diameter can be reduced.

  Further, the aperture 4 is disposed on a path through which the laser light emitted from the light source 2 passes to reach the polarization beam splitter 5. For this reason, when the laser light that has entered the aperture 4 from the light source 2 and is blocked from passing is reflected by the aperture 4, the reflected laser light is reflected by the polarization beam splitter 5 with the aperture 4 interposed therebetween. Heads in the direction opposite to the photodetector 9 arranged on the path through which the light passes (see the light L7 and L8). As a result, it is possible to suppress unnecessary reflected light, which is generated when the laser light emitted from the light source 2 is incident on the aperture 4, from being detected as noise by the photodetector 9 in the radar apparatus 1. Noise can be reduced.

  Furthermore, noise caused by unnecessary reflected light can be reduced without forming a through hole in the polarization beam splitter 5, and a decrease in detection accuracy of the radar apparatus 1 can be suppressed.

  In the embodiment described above, the mirror 71 is the reflecting member in the present invention, the rotating shaft 72 is the predetermined rotating shaft in the present invention, the optical scanning unit 7 is the scanning unit in the present invention, and the polarization beam splitter 5 is the first functional member in the present invention. The quarter-wave plate 6 is a second functional member in the present invention, the photodetector 9 is a light detection unit in the present invention, and the aperture 4 is a diaphragm member in the present invention.

(Second Embodiment)
A second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, parts different from the first embodiment will be described.

As shown in FIG. 2, the radar apparatus 1 of the second embodiment is the same as that of the first embodiment except that a polarizing beam splitter 100 is provided instead of the polarizing beam splitter 5.
The polarization beam splitter 100 has a function of transmitting a component having a predetermined polarization direction in the laser light incident on the polarization beam splitter 100 and reflecting a component having a polarization direction other than the predetermined polarization direction.

  The polarization beam splitter 100 is arranged so that the predetermined polarization direction matches the polarization direction of the laser light emitted from the light source 2. Furthermore, the polarization beam splitter 100 is a plate-shaped plate type, and a state in which a direction D2 perpendicular to the incident surface 101 on which the laser light is incident is inclined with respect to the incident direction of the laser light (see the inclination angle A2). Is arranged in. In the present embodiment, the inclination angle A2 is 45 °.

  In the radar apparatus 1 configured as described above, the polarization beam splitter 100 is a plate type so that the incident surface 101 on which the laser light emitted from the light source 2 is incident is not opposed to the photodetector 9. In addition, the incident direction of the laser light emitted from the light source 2 and the incident surface 101 are not perpendicular to each other. For this reason, the laser light reflected by the incident surface 101 of the polarizing beam splitter 100 travels in the direction opposite to the photodetector 9 with the polarizing beam splitter 100 interposed therebetween. Thereby, the unnecessary reflected light generated when the laser light emitted from the light source 2 is incident on the polarization beam splitter 100 is suppressed from being detected as noise by the photodetector 9 in the radar apparatus 1, and the unnecessary reflected light is suppressed. It is possible to further reduce the noise caused by.

In the embodiment described above, the polarizing beam splitter 100 is the first functional member in the present invention.
(Third embodiment)
A third embodiment of the present invention will be described below with reference to the drawings. In the third embodiment, parts different from the second embodiment will be described.

The radar apparatus 1 of the third embodiment is the same as that of the second embodiment except that an aperture 200 is provided instead of the aperture 4.
As shown in FIG. 3, the aperture 200 is a thin film member 201 having an opening 202 formed in part, and is formed on the incident surface 101 of the polarization beam splitter 100 by printing.

  In the radar apparatus 1 configured as described above, the aperture 200 is disposed on the incident surface 101 of the polarization beam splitter 100, so that the polarization beam splitter 100 and the aperture 200 are integrated. Thereby, the optical axis adjustment between the polarization beam splitter 100 and the aperture 200 can be made unnecessary, and the optical axis adjustment in the radar apparatus 1 can be simplified.

In the embodiment described above, the incident surface 101 is the first incident surface in the present invention, and the aperture 200 is the aperture member in the present invention.
(Fourth embodiment)
A fourth embodiment of the present invention will be described below with reference to the drawings. In the fourth embodiment, parts different from the third embodiment will be described.

The radar apparatus 1 of the third embodiment is the same as that of the third embodiment except that a polarization beam splitter 300 is provided instead of the polarization beam splitter 100.
As shown in FIG. 4, the polarization beam splitter 300 is formed on a plate-like substrate 301 made of a material that can transmit laser light and an incident surface 302 of the substrate 301 so as to have a polarization separation function. And the polarized light separating structure 303.

  The polarized light separating structure 303 has a plurality of fine lines formed of a conductive material (for example, Al, Au, Ag, Cu, etc.) at intervals shorter than the wavelength of the laser light emitted from the light source 2. Are arranged in parallel along a direction that coincides with the polarization direction of the light.

  The aperture 200 is formed on the incident surface 302 of the polarization beam splitter 300 by printing. The polarization separation structure 303 is formed in the opening 202 on the incident surface 302.

  According to the radar apparatus 1 configured as described above, since the polarization separation structure 303 can be formed using a fine processing technique, a cube-type polarization beam splitter that is formed in a cube shape by bonding right-angle prisms or the like Compared with the conventional polarizing beam splitter, the polarizing beam splitter can be miniaturized.

In the embodiment described above, the polarization beam splitter 300 is the first functional member in the present invention, and the polarization separation structure 303 is the fine periodic structure in the present invention.
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.

  For example, in the above-described embodiment, the polarization beam splitter 5 has the inclination angle A1 of 45 °, but may be an angle other than 45 °.

  DESCRIPTION OF SYMBOLS 1 ... Radar device, 2 ... Light source, 4,200 ... Aperture, 5,100, 300 ... Polarizing beam splitter, 6 ... 1/4 wavelength plate, 7 ... Optical scanning part, 9 ... Photo detector, 71 ... Mirror, 72 …Axis of rotation

Claims (3)

A light source (2) that emits light;
A scanning unit (7) that scans light emitted from the light source by rotating a reflecting member (71) having a function of reflecting light around a predetermined rotation axis (72) set in advance;
The first light source is disposed on a path through which the light emitted from the light source passes to reach the scanning unit, and has a function of transmitting light in a predetermined polarization direction set in advance and reflecting light in a direction other than the predetermined polarization direction. 1 functional member (5, 100, 300);
A second functional member that is disposed on a path through which light transmitted through the first functional member passes to reach the scanning unit, and has a function of converting linearly polarized light into circularly polarized light and converting circularly polarized light into linearly polarized light. (6) and
A light detection unit (9) that is disposed on a path through which light incident on the first functional member and reflected by the first functional member passes from the scanning unit side, and detects the incident light;
The light emitted from the light source is arranged on a path through which the light passes to reach the first functional member, passes a part of the light emitted from the light source, and passes light other than the part. And a diaphragm member (4,200) for restricting the diameter of the light emitted from the light source. In the first functional member (100), a surface on which light emitted from the light source is incident is defined as a first incident surface (101).
The radar apparatus according to claim 1, wherein the aperture member (200) is disposed on the first incident surface. The first functional member (300) is
A plate-shaped substrate (301) formed to be able to transmit light emitted from the light source;
A plurality of fine lines formed of a conductive material are formed in a lattice shape by being arranged on the substrate in parallel with the predetermined polarization direction at intervals shorter than the wavelength of light emitted from the light source. The radar apparatus according to claim 2, comprising a fine periodic structure (303).

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